Five Democratic senators are seeking an FBI investigation into possible cyberattacks on the Federal Communication Commission’s online comment system.

The FCC’s Electronic Comment Filing System crashed in the early hours of May 8 in what the agency called “deliberate attempts by external actors to bombard” the commission and render its systems unusable by legitimate commenters.

Sens. Brian Schatz (D-Hawaii), Al Franken (D-Minn.), Patrick Leahy (D-Vt.), Ed Markey (D-Mass.) and Ron Wyden (D-Ore.) want acting FBI director Andrew McCabe to make an investigation of that May disruption a priority, and also called for an investigation into the source of the attack. The senators’ letter emphasized that they were especially troubled by the disruption of the process of public commentary given that public participation is crucial to the integrity of the FCC’s regulatory process.

The request comes as FCC Chairman Ajit Pai is moving to roll back Obama-era net neutrality regulations over the objections of Democrats in Congress and internet freedom activists.

“Any cyberattack on a federal network is very serious,” the senators wrote. “This particular attack may have denied the American people the opportunity to contribute to what is supposed to be a fair and transparent process, which in turn may call into question the integrity of the FCC’s rulemaking proceedings.”

The senators seek a reply by June 23.

It’s possible, however, that what the FCC is reporting as a DDoS attack was in fact a traffic spike spurred by TV comedian John Oliver, who urged viewers to register their opposition to the net neutrality rollback in an May 7 broadcast.

The partisan fight over FCC actions on net neutrality has cast a political shadow over the attack, the follow-up and any future investigation. Three of the letter’s five signatories (Schatz, Markey, Franken) also signed a May 17 open letter lambasting the FCC’s possible net neutrality rollback.

Wyden and Schatz also sought clarification from Pai about the ability of the agency to protect against DDoS attacks in a separate May 9 letter. The two sought details on the user capacity of the FCC’s website and requested a reply by June 8.

Meanwhile, the FCC is accepting comments on its net neutrality proceeding through Aug. 16.